Coke slurry fuel composition and method of making the same

ABSTRACT

A coke slurry fuel composition of the instant disclosure comprises 40-80 percentage by weight of petroleum coke (dry basis), 20-60 percentage by weight of biological sludge (wet basis), and 1-4 percentage by weight of basic additive. Accordingly, the coke slurry fuel composition with high combustion efficiency can be adapted to reduce emissions of toxic or air pollutants, and the purpose of sludge reduction can also be achieved. A method of making coke slurry fuel composition is further provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The instant disclosure relates to fuel technologies; in particular, to a coke slurry fuel composition and method of making the same.

2. Description of Related Art

With the quick development of society and economies in modern society, the world is facing serious shortages of energy. According to statistics, the world oil reserves are, if current consumption levels continue, expected to exhaust within 50 years. The world's total proved coal reserves are expected to exhaust within 100 years. The countries of the world are finding and developing alternative energy. For this reason people start looking for renewable energy.

Petroleum coke (often abbreviated pet coke or petcoke) is a by-product of the oil refining process, resulted from the thermal processing of residual oil, which has been cracked or otherwise processed to remove low boiling fractions. Petroleum coke is a carbon-based material composed of crystallized graphite which may form in a variety of shapes, e.g., particles, cylinders, and needles. The chemical composition of petroleum coke is composed primarily of carbon (carbon content of greater than about 80 wt %) along with variable quantities of other elements, chiefly hydrogen, oxygen, nitrogen, and sulfur. Petroleum coke generally has high hydrogen to carbon atomic ratio (H/C) range between 18 and 24 and a specific gravity range between 0.9 and 0.11, and the calorific value of combustion is in the range between 8000 kcal/L to 8500 kcal/L.

With the rising awareness of environmental protection in recent years, the requirements for pretreatment and disposal of sewage sludge have become high. The sewage sludge production in Taiwan is expected to reach 4 million tons, and the volume of generated sludge has increased each year at a growth rate of 20% per year. However, the amount of sewage sludge for disposal in landfills is expected to increase. Disposal of the partially dried sludge can be effected by converting it to fertilizer for agricultural purposes, burning it or gasifying the sludge. The sewage sludge production has caused serious impact on the humans and the environment in which we are living. Taiwan's landfills will be exhausted soon. There is serious need for some solutions and to come up with some ideas to solve the problem.

Due to the larger proportion of city's sewer system (the city's progressive administration), the amount of domestic sewage water has relatively increased, thus reducing the amount of organic sludge generated by biological treatment processes. For the city's sewer system in Taiwan, the organic sludge has been produced at production rates of 210 tons per day so far in 2003. “Biological sludge” generally consists of old microorganisms (also called sludge floes) produced biologically by aerobic bacteria in the biological oxidation processes. The old microorganisms which cannot be easily dewatered by mechanical force due to its structure such as sponge-shaped structures. Biological sludge after dewatering by the pressure filter still has a water content of about 80%. Moreover, biological sludge contains large amounts of organic matter, and the heat of combustion is in the range between 3500 kcal/L to 4000 kcal/L. The fuel quality would be almost equal to coal fuel.

However, due to its very high water content, biological sludge cannot be used for direct co-firing with solid fuel. Biological sludge disposal is a growing worldwide problem. For this reason, biological sludge is mainly disposed by landfilling, composting, recycling, incinerating, and calcining.

Following are the disadvantages of the afore-mentioned disposal means. Biogas can be produced from biological sludge in a landfill, thus polluting the ground water. The organic fertilizer or soil amendment product made from biological sludge is a risk to human and environmental health because biological sludge contains harmful substances such as pathogenic bacteria, heavy metals, and carcinogenic compounds. Further, the disposal method of incineration cannot achieve high thermal efficiency due to energy balance problems. Besides, the lightweight aggregate made from biological sludge cannot meet the market requirements due to the higher production cost and technology.

There is a sludge reduction system that uses anaerobic bacteria. However, methane gas (CH₄) and toxic hydrogen sulfide gas (H₂SO₄) can be produced in the biological digestion process, and the methane gas will react with the hydrogen sulfide gas to form sulfuric acid when combustion occurs. The generated fuel gas must be desulfurized before recycling. There is also a sludge reduction system that uses aerobic bacteria.

SUMMARY OF THE INVENTION

In view of increasing shortage of global energy resources and the disadvantages of the conventional sludge reduction technologies, the object of the instant disclosure is to provide a coke slurry fuel composition and a method of making the same. The instant coke slurry fuel composition is configured in support of reducing the amount of sludges produced in the city's sewer system and substances in sludges which are harmful to the environment and saving energy.

In order to achieve the aforementioned objects, according to an embodiment of the instant disclosure, the coke slurry fuel composition, having a burnout rate of at least 97%, comprises (a) petroleum coke, (b) biological sludge, and (c) a basic additive, wherein the content of the component (a) is 40 wt % to 80 wt % on a dry basis, the content of the component (b) is 20 wt % to 60 wt % on a wet basis, and the content of the component (c) based on the entire amount of components (a) and (b) is 1 wt % to 4 wt %, and wherein the component (c) is added to control the sulfur-oxygen compounds (SOx) generated by the burning of the coke slurry fuel composition, whereby the content of SOx in the flue gas is less than about 150 ppm.

One of the embodiments of the instant disclosure provides a method of making coke slurry fuel composition that comprises: providing petroleum coke pellets and biological sludges; feeding a cluster of petroleum coke pellets into a slurry of the biological sludges in a predetermined ratio according to a desired calorific value to form a fuel precursor, and then agitating and grinding the fuel precursor simultaneously to form a petroleum coke-based fuel slurry; and screening the petroleum coke-based fuel slurry.

Another one of the embodiments of the instant disclosure provides a method of making coke slurry fuel composition that comprises: providing petroleum coke pellets and biological sludges; dry-grinding the petroleum coke pellets into particles and wet-grinding a slurry of the biological sludges into a fine organic-rich slurry, and then screening the petroleum coke particles; feeding and mixing a cluster of the screened petroleum coke particles with the fine organic-rich slurry in a predetermined ratio according to a desired calorific value to form a petroleum coke-based fuel slurry; and screening the petroleum coke-based fuel slurry.

Still another one of the embodiments of the instant disclosure provides a method of making coke slurry fuel composition that comprises: providing petroleum coke pellets and biological sludges; wet-grinding the petroleum coke pellets to form a water slurry of petroleum coke and wet-grinding a slurry of the biological sludges into a fine organic-rich slurry, and then screening the water slurry of petroleum coke and the fine organic-rich slurry; and feeding and mixing the screened water slurry of petroleum coke with the screened fine organic-rich slurry in a predetermined ratio according to a desired calorific value.

To sum up, the instant coke slurry fuel composition, in which petroleum coke as a source of energy is adapted to co-work with biological sludge, can be used to replace the conventional solid fuel. Thus, the amount of sludge and its disposal cost can be reduced.

Further, the instant coke slurry fuel composition contains a specific percentage of a basic additive, wherein the basic additive can be in any suitable form for reacting sulfur-containing substances to form sodium sulfide particles. Sulfur molecules with electrons in this way cannot react with the oxygen atoms, and the production of the exhaust gas containing the sulfur oxide (SOx) can be reduced.

Furthermore, there is no need to consider the sulfur content of the petroleum coke pellets in the combustion process. In other words, the coke slurry fuel composition made by the instant method can overcome the limitation of the quality and purity of petroleum coke without desulfurization.

In order to further appreciate the characteristics and technical contents of the instant disclosure, references are hereunder made to the detailed descriptions and appended drawings in connection with the instant disclosure. However, the appended drawings are merely shown for exemplary purposes, rather than being used to restrict the scope of the instant disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram illustrating the method of making a coke slurry fuel composition in accordance with a first embodiment of the instant disclosure;

FIG. 2 is a flow diagram illustrating the method of making a coke slurry fuel composition in accordance with a second embodiment of the instant disclosure; and

FIG. 3 is a flow diagram illustrating the method of making a coke slurry fuel composition in accordance with a third embodiment of the instant disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a resource recycling means for improving energy efficiency and solving the problems of a huge quantity of sludge generation and the high treatment cost thereof. Thus, biological sludges generated in wastewater treatment processes can be minimized. Specifically, said biological sludges can be used to co-work with a premium “fuel-grade” petroleum coke produced by modifying petroleum coking technology, in this way an environmentally friendly aqueous fuel can be prepared. Moreover, the aqueous fuel having a calorific value of at least 4500 kcal/L can be used to replace the conventional coal based solid fuel.

The aforementioned illustrations and following detailed descriptions are exemplary for the purpose of further explaining the scope of the instant disclosure. Other objectives and advantages related to the instant disclosure will be illustrated in the subsequent descriptions and appended drawings.

The First Embodiment

Please refer to FIG. 1, a method of making coke slurry fuel composition in accordance with a first preferred embodiment is provided. The method comprises the steps of: providing petroleum coke pellets and biological sludges (S100); feeding a cluster of petroleum coke pellets into a slurry of biological sludge in a predetermined ratio according to a desired calorific value to form a fuel precursor, and then agitating and grinding the fuel precursor simultaneously to form a petroleum coke-based fuel slurry (S102); and screening the petroleum coke-based fuel slurry (S104).

Step S100 is to provide petroleum coke pellets and biological sludges. The petroleum coke pellets can comprise a combination of more than one type of solid coke product, i.e., needle coke, sponge coke, spherical coke and shot coke. The biological sludges can be derived from domestic sewage, industrial sewage, animal sewage, municipal sewage, or the combination thereof. The biological sludges obtained in decomposition of the sewage by micro-organisms have high water content, especially rich in organic matter.

It should be noted that there is no need to consider the sulfur content of the petroleum coke pellets in the combustion process. In other words, the coke slurry fuel composition made by the instant method can overcome the limitation of the quality and purity of petroleum coke without desulfurization. Moreover, petroleum coke pellets and biological sludges are complementary in their physical and chemical properties. Thus, the biological sludges acting as a secondary fuel can bind the petroleum coke pellets together to compose a novel aqueous fuel.

Step S102 is to feed a cluster of petroleum coke pellets into a slurry of biological sludge in a predetermined ratio according to a desired calorific value to form a fuel precursor, and then to agitate and grind the fuel precursor simultaneously to form a petroleum coke-based fuel slurry. In practice, the cluster of petroleum coke pellets is firstly mixed into the slurry of biological sludge. The content of the petroleum coke pellets is 40 wt % to 80 wt % on a dry basis. The content of the biological sludge is 20 wt % to 60 wt %. Next, the fuel precursor is agitated and ground adequately by wet ball-milling. Preferably, a processing aid and a basic additive can be added to increase the grinding efficiency and accuracy. The content of the processing aid based on the entire amount of the fuel precursor is 1 wt % to 5 wt %. The content of the basic additive based on the entire amount of the fuel precursor is 0.5 wt % to 2.5 wt %.

It should be noted that the coke slurry fuel composition is usually adequate to meet the processing requirements for the reduction of gutter oil and activated carbon waste or reactive coke. Specifically, gutter oil having a calorific value in the range between 9300 kcal/L to 9500 kcal/L and activated carbon waste (reactive coke) having a calorific value in the range between 4500 kcal/L to 4700 kcal/L can also be fed when mixing the petroleum coke pellets in firstly with the biological sludge. The content of the gutter oil based on the entire amount of the fuel precursor is 5 wt % to 20 wt %. The content of the activated carbon waste (reactive coke) based on the entire amount of the fuel precursor is 1 wt % to 20 wt %.

For the instant embodiment, the processing aid, acting as a stabilizing and dispersing agent, can be selected from the group consisting of ligninsulfonate, naphthalenesulfonic acid, sodium polyacrylate acid, poly(styrenesulfonic acid), carboxymethyl cellulose. The basic additive can be selected from the group consisting of sodium carbonate, sodium hydroxide, sodium silicate, sodium tripolyphosphate, and the combination thereof. The basic additive can function as a peptizer, configured to remove oil or colloidal material from the petroleum coke-based fuel slurry in the wet ball-milling process, thus having a viscosity less than 1250 mPa*s at 20° C.

Step S102 is to screen the petroleum coke-based fuel slurry. In practice, the petroleum coke-based fuel slurry is recycled through the 200 mesh screen. The instant coke slurry fuel composition can accordingly be completed simply by being screened.

The Second Embodiment

Please refer to FIG. 2, a method of making coke slurry fuel composition in accordance with a second preferred embodiment is provided. The method comprises the steps of: providing petroleum coke pellets and biological sludges (S200); dry-grinding the petroleum coke pellets into particles and wet-grinding a slurry of the biological sludges into a fine organic-rich slurry, and then screening the petroleum coke particles (S202); feeding and mixing a cluster of the screened petroleum coke particles with the fine organic-rich slurry in a predetermined ratio according to a desired calorific value to form a petroleum coke-based fuel slurry (S204); and screening the petroleum coke-based fuel slurry (S206).

Step S200 is to provide petroleum coke pellets and biological sludges. Similarly, the petroleum coke pellets can comprise a combination of more than one type of solid coke product, i.e., needle coke, sponge coke, spherical coke and shot coke, where the shape is not restricted to any specific form. The biological sludges can be derived from domestic sewage, industrial sewage, animal sewage, municipal sewage, or the combination thereof. The biological sludges obtained in decomposition of the sewage by micro-organisms have high water content, especially rich in organic matter. Please note, the properties and advantages of the petroleum coke pellets and the biological sludges are fully described in the first embodiment, the repetitious details need not be given here.

Step S202 is to dry-grind the petroleum coke pellets into particles and wet-grind a slurry of the biological sludges into a fine organic-rich slurry, and then to screen the petroleum coke particles. In practice, the petroleum coke pellets can be ground into particles that have a desired particle size distribution by any suitable dry-grinding means, i.e., crusher, pulverizer, muller, and ball grinder, where the dry-grinding means is not restricted thereto. Moreover, the petroleum coke particles should pass through the 200 mesh screen to maintain those which have an average particle size in the range between 40 μm to 50 μm, preferably about 45 μm. Therefore, the petroleum coke particles having a desired particle size distribution can be carried by the slurry in stable suspension.

The cell walls and cell membranes of the biological materials in the slurry of the biological sludges can be ruptured by wet ball-milling in the presence of a basic additive in an amount in the range of 0.5% to 2.5%. Please note, the properties and advantages of the basic additive are fully described in the first embodiment; the repetitious details need not be given here.

Step S204 is to feed a cluster of the screened petroleum coke particles into the fine organic-rich slurry in a predetermined ratio according to a desired calorific value, and then to mix adequately to form a petroleum coke-based fuel slurry. In practice, the cluster of the screened petroleum coke particles can be adequately mixed with the fine organic-rich slurry by any suitable mixing apparatus, preferably in the presence of a processing aid. The content of the petroleum coke is 40 wt % to 80 wt % on a dry basis. The content of the biological sludges is 20 wt % to 60 wt %. The content of the processing aid based on the entire amount of the fuel precursor is 1 wt % to 4 wt %. Please note, the properties and advantages of the processing aid are fully described in the first embodiment; the repetitious details need not be given here.

It should be noted that the coke slurry fuel composition is usually adequate to meet the processing requirements for the reduction of gutter oil and activated carbon waste or reactive coke. Specifically, gutter oil and activated carbon waste (reactive coke) can also be fed when mixing the screened petroleum coke particles into the fine organic-rich slurry. The content of the gutter oil based on the entire amount of the petroleum coke pellets and the biological sludges is 5 wt % to 20 wt %. The content of the activated carbon waste (reactive coke) based on the entire amount of the petroleum coke pellets and the biological sludges is 1 wt % to 20 wt %.

Step S206 is to screen the petroleum coke-based fuel slurry. In practice, the petroleum coke-based fuel slurry is recycled through the 200 mesh screen. The instant coke slurry fuel composition can accordingly be completed simply by being screened.

The Third Embodiment

Please refer to FIG. 3, a method of making coke slurry fuel composition in accordance with a third preferred embodiment is provided. The method comprises the steps of: providing petroleum coke pellets and biological sludges (S300); wet-grinding the petroleum coke pellets to form a water slurry of petroleum coke and wet-grinding a slurry of the biological sludges into a fine organic-rich slurry, and then screening the water slurry of petroleum coke and the fine organic-rich slurry (S302); and feeding and mixing the screened water slurry of petroleum coke with the screened fine organic-rich slurry in a predetermined ratio according to a desired calorific value to form a petroleum coke-based fuel slurry (S304).

Step S300 is to provide petroleum coke pellets and biological sludges. Similarly, the petroleum coke pellets can comprise a combination of more than one type of solid coke product, i.e., needle coke, sponge coke, spherical coke and shot coke, where the shape is not restricted to any specific form. The biological sludges can be derived from domestic sewage, industrial sewage, animal sewage, municipal sewage, or the combination thereof. The biological sludges obtained in decomposition of the sewage by micro-organisms have high water content, especially rich in organic matter. Please note, the properties and advantages of the petroleum coke pellets and the biological sludges are fully described in the first embodiment, the repetitious details need not be given here.

Step S302 is to wet-grind the petroleum coke pellets to form a water slurry of petroleum coke and wet-grind a slurry of the biological sludges into a fine organic-rich slurry, and then to screen the water slurry of petroleum coke and the fine organic-rich slurry. In practice, the petroleum coke pellets can be ground by wet ball mills in the presence of a processing aid to form water slurry of petroleum coke. The content of the processing aid based on the entire amount of the petroleum coke pellets and the biological sludges is 1 wt % to 4 wt %. Moreover, the water slurry of petroleum coke and the fine organic-rich slurry should recycle through the 200 mesh screen, so that the petroleum coke particles having a desired particle size distribution can be carried by the slurry in stable suspension.

Step S304 is to feed and mix the screened water slurry of petroleum coke with the screened fine organic-rich slurry in a predetermined ratio according to a desired calorific value to form petroleum coke-based fuel slurry. The content of the petroleum coke is 40 wt % to 80 wt % on a dry basis, and the content of the biological sludges is 20 wt % to 60 wt %. Further processing aid can be added to the mixture of the screened water slurry of petroleum coke and the screened fine organic-rich slurry. The content of the basic additive based on the entire amount of the fuel precursor is 0.5 wt % to 2.5 wt %. The instant coke slurry fuel composition can accordingly be completed simply by mixing adequately. Please note, the properties and advantages of the processing aid are fully described in the first embodiment; the repetitious details need not be given here.

It should be noted that the coke slurry fuel composition is usually adequate to meet the processing requirements for the reduction of gutter oil and activated carbon waste or reactive coke. Specifically, gutter oil and activated carbon waste (reactive coke) can also be fed when mixing the screened water slurry of petroleum coke with the screened fine organic-rich slurry. The content of the gutter oil based on the entire amount of the petroleum coke pellets and the biological sludges is 5 wt % to 20 wt %. The content of the activated carbon waste (reactive coke) based on the entire amount of the petroleum coke pellets and the biological sludges is 1 wt % to 20 wt %.

The processing steps of the method of making coke slurry fuel composition and the operating conditions of each processing step are fully described, as noted above. The following will further describe the coke slurry fuel composition made by the method, which comprises: (a) petroleum coke, (b) biological sludge, (c) a basic additive, (d) gutter oil, and (e) activated carbon waste or reactive coke. The content of the component (a) is 40 wt % to 80 wt % on a dry basis. The content of the component (b) is 20 wt % to 60 wt % on a wet basis. The content of the component (c) based on the entire amount of components (a) and (b) is 1 wt % to 4 wt %. The content of the component (d) based on the entire amount of components (a) and (b) is 5 wt % to 20 wt %. The content of the component (e) based on the entire amount of components (a) and (b) is 1 wt % to 20 wt %.

Please note, the coke slurry fuel composition comprises predetermined main components of petroleum coke and biological sludge. Any other subcomponent, with respect to 100 wt % of said main component, can be added to the composition if it is preferred to enhance aqueous fuel properties.

Based on the above, the instant coke slurry fuel composition contains only very low levels of sulfur and nitrogen. Moreover, the instant coke slurry fuel composition contains a specific percentage of a basic additive, wherein the basic additive can be in any suitable form for reacting sulfur-containing substances to form sodium sulfide particles. Accordingly, sulfur molecules with electrons from the sulfur-containing substances cannot react with the oxygen atoms to form sulfur-oxygen compounds (SOx), and the concentration of nitrogen-oxygen compounds (NOx) in combustion can be reduced. According to statistics, the sulfur-oxygen compounds (SOx) generated by the burning is less than about 150 ppm, and the nitrogen-oxygen compounds (NOx) generated by the burning is less than about 30 ppm.

Most of all, biological sludges, gutter oil and activated carbon waste or reactive coke acting as a secondary fuel can co-work with petroleum coke, thus the instant coke slurry fuel composition is usually adequate to meet the processing requirements for the reduction of gutter oil and activated carbon waste or reactive coke.

The descriptions illustrated supra set forth simply the preferred embodiments of the instant disclosure; however, the characteristics of the instant disclosure are by no means restricted thereto. All changes, alterations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the instant disclosure delineated by the following claims. 

What is claimed is:
 1. A coke slurry fuel composition, having a burnout rate of at least 97%, comprising (a) petroleum coke, (b) biological sludge, and (c) a basic additive; wherein the content of the component (a) is 40 wt % to 80 wt % on a dry basis, the content of the component (b) is 20 wt % to 60 wt % on a wet basis, and the content of the component (c) based on the entire amount of components (a) and (b) is 1 wt % to 4 wt %; wherein the component (c) is added to control the sulfur-oxygen compounds (SOx) generated by the burning of the coke slurry fuel composition, whereby the content of SOx in the fuel gas is less than about 150 ppm.
 2. The coke slurry fuel composition according to claim 1, wherein the component (b) is derived from domestic sewage, industrial sewage, animal sewage, municipal sewage, or the combination thereof.
 3. The coke slurry fuel composition according to claim 1, wherein the component (c) is selected from the group consisting of sodium carbonate, sodium hydroxide, sodium silicate, sodium tripolyphosphate, and the combination thereof.
 4. The coke slurry fuel composition according to claim 3, having a water content in the range of 35% to 42% and a viscosity less than 1250 mPa*s at 20° C.
 5. The coke slurry fuel composition according to claim 4, the nitrogen-oxygen compounds (NOx) generated by the burning of which is less than about 30 ppm.
 6. The coke slurry fuel composition according to claim 5, further comprising (d) gutter oil and (e) activated carbon waste or reactive coke, the content of the component (d) based on the entire amount of components (a) and (b) is 5 wt % to 20 wt %, and the content of the component (e) based on the entire amount of components (a) and (b) is 1 wt % to 20 wt %.
 7. A method of making coke slurry fuel composition, comprising the following steps: providing petroleum coke pellets and biological sludges; feeding a cluster of petroleum coke pellets into a slurry of biological sludge in a predetermined ratio according to a desired calorific value to form a fuel precursor, and then agitating and grinding the fuel precursor simultaneously to form a petroleum coke-based fuel slurry; and screening the petroleum coke-based fuel slurry.
 8. The method according to claim 7, wherein the fuel precursor is agitated and ground adequately by wet ball-milling in the present of a processing aid in an amount in the range of 1% to 5% and a basic additive in an amount in the range of 0.5% to 2.5% in the step of feeding a cluster of petroleum coke pellets into a slurry of biological sludge.
 9. The method according to claim 8, wherein the processing aid is selected from the group consisting of ligninsulfonate, naphthalene sulfonic acid, sodium polyacrylate acid, poly(styrenesulfonic acid), carboxymethyl cellulose, and the combination thereof, and the basic additive is selected from the group consisting of sodium carbonate, sodium hydroxide, sodium silicate, sodium tripolyphosphate, and the combination thereof.
 10. A method of making coke slurry fuel composition, comprising the following steps: providing petroleum coke pellets and biological sludges; dry-grinding the petroleum coke pellets to form petroleum coke particles and wet-grinding the biological sludge to form a microalgal slurry, and then screening the petroleum coke particles; feeding a cluster of the screened petroleum coke particles into the microalgal slurry in a predetermined ratio according to a desired calorific value, mixing adequately, to form a petroleum coke-based fuel slurry; and screening the petroleum coke-based fuel slurry.
 11. The method according to claim 10, wherein the biological sludges are adequately ground by wet ball-milling to rupture the microalgae cells and form the microalgal slurry in the presence of a basic additive in an amount in the range of 0.5% to 2.5% in the step of wet-grinding the biological sludge to a desired size.
 12. The method according to claim 11, wherein the screened petroleum coke particles is mixed adequately with the microalgal slurry in the presence of a processing aid in an amount in the range of 1% to 4% in the step of feeding a cluster of the screened petroleum coke particles into the microalgal slurry.
 13. The method according to claim 12, wherein the processing aid is selected from the group consisting of ligninsulfonate, naphthalene sulfonic acid, sodium polyacrylate acid, poly(styrenesulfonic acid), carboxymethyl cellulose, and the combination thereof, and the basic additive is selected from the group consisting of sodium carbonate, sodium hydroxide, sodium silicate, sodium tripolyphosphate, and the combination thereof.
 14. A method of making coke slurry fuel composition, comprising the following steps: providing petroleum coke pellets and biological sludges; wet-grinding the petroleum coke pellets and the biological sludges respectively to form a petroleum coke slurry and a microalgal slurry, and screening the petroleum coke slurry and the microalgal slurry; and feeding the screened petroleum coke slurry and the screened microalgal slurry in a predetermined ratio according to a desired calorific value, mixing adequately, to form a petroleum coke-based fuel slurry.
 15. The method according to claim 14, wherein the petroleum coke pellets are adequately ground to a desired size, and the biological sludges are adequately ground to rupture the microalgae cells and form the microalgal slurry in the presence of a processing aid in an amount in the range of 1% to 4% in the step of wet-grinding the petroleum coke pellets and the biological sludges respectively.
 16. The method according to claim 15, wherein the screened petroleum coke slurry are mixed with the screened microalgal slurry adequately in the presence of a basic additive in an amount in the range of 0.5% to 2.5% in the step of feeding the screened petroleum coke slurry and the screened microalgal slurry.
 17. The method according to claim 16, wherein the screened petroleum coke particles are mixed adequately with the microalgal slurry in the presence of a processing aid in an amount in the range of 1% to 5% in the step of feeding a cluster of the screened petroleum coke particles into the microalgal slurry. 